LEPTOSPIROSIS / WEIL'S SYNDROME / CANICOLA FEVER / CANEFIELD OR PADDYFIELD FEVER / NANUKAYAMI FEVER / 7-DAY FEVER / RAT CATCHER'S YELLOWS / FORT BRAGG

LEPTOSPIROSIS / WEIL'S SYNDROME / CANICOLA FEVER / CANEFIELD OR PADDYFIELD FEVER / NANUKAYAMI FEVER / 7-DAY FEVER / RAT CATCHER'S YELLOWS / FORT BRAGG FEVER / PRETIBIAL FEVER

Introduction:

Leptospirosis or LEPTO, is one of the commonest seasonal spirochaetal zoonoses in tropical countries with heavy rainfall like India, where flooding and waterlogging are fairly common. With its humid climate, heavy rainfall, waterlogging, water retaining aluvial soil, paddy feild work and an abundance of domestic and stray cattle, dogs and especially rodents, regios like the south Konkan region is naturally an endemic region for this disease.

The disease was first described by Adolf Weil in 1886 when he reported an "acute infectious disease with enlargement of spleen, jaundice and nephritis" and hence, is also called as Weil's Syndrome.

Human leptospirosis can range from a mild febrile illness to the fatal Spirochaetal Jaundice of Weil.

Timely diagnosis and treatment is crucial for early recovery from the disease and avoidance of complications.

Causative Agent:

Human Leptospirosis is caused by many strains of Leptospira interrogans, a 5 - 15 micron spirochaete with hooked ends. Till now, 23 serogroups and 200 serovers have been recognized throughout the world. They are serologically related with cross reactivity.

Transmission:

Leptospirosis, being a zoonosis, affects both humas and animals.

Animal to man transmission is the commonest mode. Man to man transmission is rare.

Leptospira are excreted in the urine of the infected animal for a long time. So much so, that an infected rodent excretes leptospira in its urine for the remainder of its life.

These Leptospira remain infectious as long as they are in a moist medium.

Direct contact with this urine or infected animal tissue acts as a direct source of infection.

This infected urine might enter a still waterbody like a puddle, pool, pond or lake or wet clay/mud ( chikkhal ) where these leptospira thrive and wait for a new host.

Besides these, moist surfaces, soil and organic matter coming in contact with the infected urine also act as an indirect source of infection.

If abraded/incised/lacerted/ulcerated skin comes in contact of such a contaminated source, leptospira gain entry into the body of the new host.

Although Leptospira cannot penetrate intact skin, intact mucous membranes can be easily penetrated.

Ingestion of contaminated food or water also acts as a portal of entry for leptospira.

Thus, desquamated skin, eyes, mouth, nose and the alimentary canal are the most vulnerable sites of infection.

Droplet infection may also occur by inhlation of spray of infected urine or milk as when milking an infected cow.

Animal Reservoirs:

1) Rodents like the domestic and field mouse, rats, moles, squirrels, hares and rabbits.

2) Domestic and stray cattle like cows and buffaloes.

3) Horses, mules and donkeys.

4) Goats, Sheep, Pigs and Dogs.

5) Wild beasts.

Rodents, particularly, Mus musculus (House mouse) and Rattus norvegicus (Brown rat) are the most important reservoirs of infection.

Children are more prone to aquire infection from pets.

At risk Individuals:

1) Patients with open leg injury like abrasion/ulcer/laceration.

2) Barefoot walkers and football players ( especially school children ).

3) Farmers and Paddy field workers.

4) Sanitary, cleaning and maintenance workers.

5) Shore fishermen, urchins, clotheswashers, swimmers and open-air bathers.

6) Livestock farmers animal handlers and butchers.

7) Garbage handlers and ragpickers.

8) Children playing in the mud and consuming food without washing their hands.

8) Veterinarians and Medical staff.

Old patients, immunocompromised individuals, diabetics, alcoholics and patients with existing hepatic and renal disease are more prone to develop complications in a shorter duration of illness.

Incubation Period:

4 - 20 days ( 10 days on an average )

Symptoms and signs:

Leptospirosis manifests itself in a wide variety of ways depending on the magnitude of infection, strain virulence and host resistance. Many cases of leptospirosis are misdiagnosed as influenza in the early period due to similarity in symptoms. The disease presents in two phases often separated by an asymptomatic interval. The first phase consists of flulike symptoms while the second phase consists of serious systemic manifestations. Diagnosis and treatment during the first phase is followed by speedy recovery and none or less systemic complications. Common symptoms and signs are listed below.

First Phase:

1) mild to high fever

2) mild to severe headache

3) mild to moderate myalgia

4) chills

5) mild eye redness to conjunctival injection

6) mild to severe abdominal pain

7) nausea and vomitting

8) skin rash

9) diarrhoea

Second Phase: ( Weil's disease )

10)jaundice

11)systemic haemorrhagic manifestations, first evident in the mucous membranes and skin as purpurae.

12)Splenomegaly

13)Nephritis

14)Meningitis

*Weil's disease or Spirochaetal jaundice of Weil can be prevented by early diagnosis and treatment.

Complications:

1) Severe Haemorrhage

2) Hepetic Failure

3) Renal Filure

4) Meningitis

Diagnosis:

Clinical diagnosis alone is not possible practically since no symptom or sign is unique to leptospirosis. Laboratory investigations are indispensible for a confirmed diagnosis.

But this increases the importance of a detailed history, atleast pertaining to the risk factors of leptspirosis, to identify a high risk patient.

It is always wiser to assume that a patient has leptospirosis, if he falls in the high risk group and presents with fever with or without the other signs of leptospirosis and no other non-leptospirosis symptom/sign. In such a case, treatment must be initiated immediately, without waiting for the lab reports. This can prove to be crucial in avoiding further progress of the disease.

And since common broad spectrum antibiotics like penicillin, tetracycline and doxycycline are used in the treatment, empirical therapy till lab confirmation is acceptable and might prove lifesaving.

Differential Diagnosis:

1) Influenza

2) Dengue and other haemorrhagic fevers.

3) Hepatitis of various etiologies.

4) Viral meningitis

5) Malaria

6) Enteric Fever

Laboratory Tests:

The organism can be isolated from the infected patient's blood duing the first 7 - 10 days.

The organism is excreted in the urine from the 10th day to 6 weeks.

Using these samples, the organism can be directly observed under the light microscope through dark-field illumination and silver staining.

The organism can also be cultured on a semisolid medium. Culture takes 1 - 6 weeks to become positive.

Diagnosis is usually made using the following serological tests:

1) IgM ELISA may be positive as early as from Day 2 of illness.

2) Microscopic Agglutination Test (MAT) using live organism and Macroscopic Agglutination using killed organism become positive from Day 7-10 and peak at 3-4 weeks and may persist at a high level for many years. MAT is considered the gold standard for diagnosis.

3) Indirect Haemagglutination

4) Immunofluorescent Antibody Assay

5) PCR

Leptodipstick test is also available nowadays.

Treatment:

Penicillin is the drug of choice and is administered in the dose of 6 million units IV daily in single or divided doses ( recommended ) for 7 days.

In Penicillin sensitive individuals, Tetracycline and Doxycycline ( 100mg b.i.d. PO x 7 days )may be prescribed.

Doxycycline ( 200mg to 250mg weekly ) may be given prophylactically to individuals at risk.

Supportive symptomatic treatment and treatment of complications as need arises.

Monitor Se. Potassium and Phosphorus to prevent hyperkalemia and hyperphosphatemia in patients with renal complications.

Severe cases may require Dialysis and Platelet transfusion and hence, timely referral of such cases to a tertiary care Hospital is a must, with prior intimation to the hospital via phone/fax to avoid transit delay.

Preventive Measures:

Vaccination against one strain of leptospira may not protect against infection against another. A vaccine incorporting all the strains of the serotypes endemic to any region is not available.

So personal safety measures are a must. These are listed as under:

1) Prevention of exposure to contaminated water.

2) Avoid barefoot walking/handling of wastes with bare hands.

3) Occupational safety measures like coveralls, boots, gloves, masks and goggles.

4) Avoidance of swimming/washing/bathing in potentially contaminated water.

5) Using urinals for urination.

6) Boiling and chlorinating drinking and cooking water.

7) Proper handling and disposal of excreta and wastes of Lepto patients.

8) Rodent control.

9) Preventing children from playing in moist soil and puddles.

10)Proper hand hygiene.

11)Vaccination of pets, domestic livestock and cattle against leptospirosis.

12)Proper sanitation

13)Doxycycline prophylaxis for high risk patients.

14)Take seminars of private and PHC doctors and create mass awareness.

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